package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author 13771
 * @date 2020/7/23 13:56
 * @description
 */
public class SimpleExecutor implements Executor{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //JDBC代码
        //1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        //2.获取Sql语句: select * from user where id = #{id} and username = #{username}
        //需要转换成JDBC可以识别的sql:select * from user where id = ? and username = ?,转换过程中，还需要对#{}里面的值进行解析
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
          //获取参数的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

        //5.执行Sql
        ResultSet resultSet = preparedStatement.executeQuery();

        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();

        //6.封装返回结果集
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <=metaData.getColumnCount() ; i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }

        return (List<E>) objects;
    }

    @Override
    public void update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {

        //JDBC代码
        //1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        //2.获取Sql语句: select * from user where id = #{id} and username = #{username}
        //需要转换成JDBC可以识别的sql:select * from user where id = ? and username = ?,转换过程中，还需要对#{}里面的值进行解析
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        //获取参数的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        for (int i = 0; i < parameterMappings.size(); i++) {
            if (parameterTypeClass.equals(java.lang.Integer.class) ||
                parameterTypeClass.equals(java.lang.String.class) ||
                parameterTypeClass.equals(java.lang.Byte.class) ||
                parameterTypeClass.equals(java.lang.Short.class) ||
                parameterTypeClass.equals(java.lang.Long.class) ||
                parameterTypeClass.equals(java.lang.Double.class) ||
                parameterTypeClass.equals(java.lang.Character.class) ||
                parameterTypeClass.equals(java.lang.Float.class) ||
                parameterTypeClass.equals(java.lang.Boolean.class)){
                preparedStatement.setObject(i + 1, params[0]);
            }else {
                ParameterMapping parameterMapping = parameterMappings.get(i);
                String content = parameterMapping.getContent();

                //反射
                Field declaredField = parameterTypeClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                Object o = declaredField.get(params[0]);
                preparedStatement.setObject(i + 1, o);
            }
        }

        //5.执行Sql
       preparedStatement.execute();
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    private BoundSql getBoundSql(String sql) {
        //标记处理类：配合标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser =
                new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        BoundSql boundSql = new BoundSql(parseSql, parameterMappingTokenHandler.getParameterMappings());
        return boundSql;
    }

}
